Multisite Photometry of the Pulsating Herbig Ae Star v346 Ori

The study of pulsation in Pre--Main--Sequence intermediate-mass stars represents an important tool for deriving information on fundamental stellar parameters and internal structure, as well as for testing current theoretical models. Interest in this class of variable stars has significantly increased during the last decade and about 30 members are presently known in the literature. AIMS: We have constructed the frequency spectrum of the oscillations in V346 Ori. We apply asteroseismic tools to these data to estimate the intrinsic parameters (mass, luminosity, effective temperature) of V346 Ori and to obtain information on its internal structure. METHODS: CCD time series photometry in the Johnson V filter has been obtained for a total of 145.7 h of observations distributed over 36 nights. The resulting light curves have been subjected to a detailed frequency analysis using updated numerical techniques. Photometric and spectroscopic data have also been acquired to determine reliable estimates of the stellar properties. RESULTS: We have identified 13 oscillation frequencies, 6 of which with higher significance. These have been compared with the predictions of non-radial adiabatic models. The resulting best fit model has a mass of 2.1±0.2 M⊙, luminosity logL/L⊙=1.37+0.11−0.13, and effective temperature 7300±200 K. These values are marginally consistent with the association of V346 Ori to Orion OB1a. Alternatively, V346 Ori could be placed at a slightly larger distance than previously estimated

Porto Oscillation Code (POSC)

The Porto Oscillation Code (POSC) has been developed in 1995 and improved over the years, with the main goal of calculating linear adiabatic oscillations for models of solar-type stars. It has also been used to estimate the frequencies and eigenfunctions of stars from the pre-main sequence up to the sub-giant phase, having a mass between 0.8 and 4 solar masses. The code solves the linearised perturbation equations of adiabatic pulsations for an equilibrium model using a second order numerical integration method. The possibility of using Richardson extrapolation is implemented. Several options for the surface boundary condition can be used. In this work we briefly review the key ingredients of the calculations, namely the equations, the numerical scheme and the output.Comment: Accepted for publication in Astrophysics and Space Science

Oral dysplastic complications after HSCT: Single case series of multidisciplinary evaluation of 80 patients

Oral squamous cell carcinoma (OSCC) is the most common secondary solid malignancy after hematopoietic stem‐cell transplantation (HSCT). OSCC following HSCT is frequently preceded by chronic graft‐versus‐host disease (cGVHD). The aim of this study was to describe a cohort of post‐HSCT patients and to evaluate the onset of oral epithelial dysplasia and/or OSCC over time. In this retrospective cohort study, we present a cohort of hematological patients that underwent HSCT. Demographic variables, clinical hematological data, data regarding acute graft‐versus‐host disease (aGVHD) and cGVHD, and oral clinical features were analyzed. We focused on clinicopathological features of a subgroup of 22 patients with oral cGVHD and OSCC after HSCT. Among 80 included patients, 46 patients (57,5%) developed aGVHD and 39 patients (48,7%) developed cGVHD. Oral mucosa was involved in 17 patients with aGVHD (36,9%) and in 22 patients (56,4%) with cGVHD. Out of a total of 22 oral biopsies, roughly 40% revealed mild to moderate dysplasia, and 32 % were OSCC. In the absence of international agreement on the best timing of oral follow‐up after HSCT, it is mandatory to establish a close multidisciplinary evaluation in order to prevent the onset of HSCT-related OSCC and to reduce post‐transplant mortality due to secondary tumors

Il lavoro della talpa. Scritti su Marx

Giuseppe Antonio Di Marco ha insegnato Filosofia della storia all’Università di Napoli Federico II, dove ha formato generazioni di studiosi dedicando la propria attività a un continuo e generoso impegno didattico. Partendo dalla teologia dialettica di Barth e Bultmann, il suo lavoro scientifico si è soffermato sul pensiero di Max Weber e in seguito su quello di Carl Schmitt. All’opera di Marx ed Engels Di Marco ha dedicato gli ultimi vent’anni di insegnamento e ricerca, trovando in questi autori la possibilità di dare risposte alla crisi dell’epoca contemporanea

A theoretical approach for the interpretation of pulsating PMS intermediate-mass stars

The investigation of the pulsation properties of pre-main-sequence intermediate-mass stars is a promising tool to evaluate the intrinsic properties of these stars and to constrain current evolutionary models. Many new candidates of this class have been discovered during the last decade and very accurate data are expected from space observations obtained for example with the CoRoT satellite. In this context we aim at developing a theoretical approach for the interpretation of observed frequencies, both from the already available ground-based observations and from the future more accurate and extensive CoRoT results. To this purpose we have started a project devoted to the computations of fine and extensive grids of asteroseismic models of intermediate mass pre-main-sequence stars. The obtained frequencies are used to derive an analytical relation between the large frequency separation and the stellar luminosity and effective temperature and to develop a tool to compare theory and observations in the echelle diagram. The predictive capabilities of the proposed method are verified through the application to two test stars. As a second step, we apply the procedure to two true observations from multisite campaigns and we are able to constrain their stellar parameters, in particular the mass, in spite of the small number of frequencies. We expect that with a significantly higher number of frequencies both the stellar mass and age could be constrained and, at the same time, the physics of the models could be tested.Comment: Accepted for publication on A&

Predicted properties of RR Lyrae stars in the SDSS photometric system

The luminosities and effective temperatures, as well as the whole bolometric lightcurves of nonlinear convective RR Lyrae models with 0.0001<Z<0.006 are transformed into the SDSS photometric system. The obtained ugriz lightcurves, mean magnitudes and colors, pulsation amplitudes and color-color loops are shown and analytical relations connecting pulsational to intrinsic stellar parameters, similarly to the ones currently used in the Johnson-Cousins filters, are derived. Finally the behaviour in the color-color planes is compared with available observations in the literature and possible systematic uncertainties affecting this comparison are discussed.Comment: accepted for publication in MNRA

Improvement of the CORS method for Cepheids radii determination based on Stromgren photometry

In this paper we present a modified version of the CORS method based on a new calibration of the Surface Brightness function in the Stromgren photometric system. The method has been tested by means of synthetic light and radial velocity curves derived from nonlinear pulsation models. Detailed simulations have been performed to take into account the quality of real observed curves as well as possible shifts between photometric and radial velocity data. The method has been then applied to a sample of Galactic Cepheids with Stromgren photometry and radial velocity data to derive the radii and a new PR relation. As a result we find log R = (1.19 +- 0.09) + (0.74 +- 0.11) log P (r.m.s=0.07). The comparison between our result and previous estimates in the literature is satisfactory. Better results are expected from the adoption of improved model atmosphere grids.Comment: 13 pages including 12 postscript figures and 3 jpeg figures; accepted for publication on A&

Matching the frequency spectrum of PMS stars by means of standard and rotating models

We applied the ATON code to the computation of detailed grids of standard (non--rotating) and rotating Pre--Main Sequence (PMS) models and computed their adiabatic oscillation spectra,with the aim of exploring the seismic properties of young stars. We adopt a method similar to the matching mode method by Guenther and Brown making use, when necessary, also of our rotating evolutionary code to compute the models for PMS stars. The method is described by a preliminary application to the frequency spectrum of two PMS stars (85 and 278) in the young open cluster NGC 6530. For the Star 85 we confirm, with self--consistent rotating models, previous interpretation of the data, attributing three close frequencies to the mode n=4, l=1 and m=0,+1,--1. For the Star 278 we find a different fit for the frequencies, corresponding to a model within the original error box of the star, and dispute the possibility thatthis star has an effective temperature much cooler that the red boundary of the radial instability strip.Comment: 9pages, 2 tables, 6 figures. Accepted to MNRA

Multisite photometry of the pulsating Herbig Ae star V346 Ori

CONTEXT: The study of pulsation in Pre--Main--Sequence intermediate-mass stars represents an important tool for deriving information on fundamental stellar parameters and internal structure, as well as for testing current theoretical models. Interest in this class of variable stars has significantly increased during the last decade and about 30 members are presently known in the literature. AIMS: We have constructed the frequency spectrum of the oscillations in V346 Ori. We apply asteroseismic tools to these data to estimate the intrinsic parameters (mass, luminosity, effective temperature) of V346 Ori and to obtain information on its internal structure. METHODS: CCD time series photometry in the Johnson V filter has been obtained for a total of 145.7 h of observations distributed over 36 nights. The resulting light curves have been subjected to a detailed frequency analysis using updated numerical techniques. Photometric and spectroscopic data have also been acquired to determine reliable estimates of the stellar properties. RESULTS: We have identified 13 oscillation frequencies, 6 of which with higher significance. These have been compared with the predictions of non-radial adiabatic models. The resulting best fit model has a mass of 2.1$\pm$0.2 $M_{\odot}$, luminosity $\log{L/L_{\odot}}=1.37^{+0.11}_{-0.13}$, and effective temperature 7300$\pm$200 K. These values are marginally consistent with the association of V346 Ori to Orion OB1a. Alternatively, V346 Ori could be placed at a slightly larger distance than previously estimated.Comment: Accepted for publication on A&A. 14 Pages, 11 Figure